[Various] obsoleting the annotate level 2 interface

[Andrew Cagney]

> As one of the GVD (see http://libre.act-europe.fr/gvd) developers, I
> confirm that to use the GDB/MI, we are waiting for a stabilized interface
> (amny things have changed til recently in MI), and the ability to
> support the command line interface for providing a regular gdb console.
> 
> Without these two critical points addressed by MI, there is no way we can
> replace annotate 1 by MI.

The proposal is to drop level-two annotation but retain level one 
indefinitly.  It is level-two that causes all the grief in the code.

Andrew